CN118418969A

CN118418969A - Brake fluid leakage detection method, vehicle controller and vehicle

Info

Publication number: CN118418969A
Application number: CN202410855060.5A
Authority: CN
Inventors: 蒋帅; 隋清海; 郝占武; 李金龙; 于善勇; 赵洪田; 耿凯峰; 那健飞
Original assignee: FAW Group Corp
Current assignee: FAW Group Corp
Priority date: 2024-06-28
Filing date: 2024-06-28
Publication date: 2024-08-02

Abstract

The invention discloses a brake fluid leakage detection method, a vehicle controller and a vehicle, and belongs to the technical field of vehicles, wherein the brake fluid leakage detection method is used for acquiring a first hydraulic volume of a servo cylinder and recording a first moment when the first actual pressure reaches a preset pressure in the process that the first actual pressure of the servo cylinder is lifted to a target pressure; in the process that the second actual pressure of the servo cylinder is gradually reduced, when the second actual pressure falls back to the preset pressure, obtaining a second hydraulic volume of the servo cylinder, and recording a second moment; presetting the hysteresis liquid requirement of a system when a vehicle leaves a factory; according to the first hydraulic volume, the second hydraulic volume and the system hysteresis liquid requirement, the volume of the leaked brake liquid in the integrated brake control system can be calculated, then the time for leaking the brake liquid is calculated according to the first moment and the second moment, and further the leakage quantity of the first brake liquid is obtained, the leakage quantity of the brake liquid can be accurately calculated, and the safe operation of the brake system of the vehicle is ensured.

Description

Brake fluid leakage detection method, vehicle controller and vehicle

Technical Field

The present invention relates to the field of vehicle technologies, and in particular, to a brake fluid leakage detection method, a vehicle controller, and a vehicle.

Background

At present, a passenger car braking system is mainly a hydraulic braking system, braking force is transmitted through a hydraulic loop, and as the braking system comprises parts such as a brake, a brake hose, a brake hard tube, a joint, an integrated brake control assembly and the like, once the parts are not well sealed in the use process, the risk of leakage exists, the brake becomes soft when the weight is light, the brake fails when the weight is heavy, and the braking safety is influenced. For a novel brake-by-wire hydraulic brake system, brake safety is particularly important.

In the prior art, the integrated brake control system is pre-stored with preset pressures corresponding to the treaded depths of different brake pedals, when a driver treads the brake pedals to control the vehicle to brake, the corresponding preset pressures are adjusted according to the treaded depths of the brake pedals, the measured pressure of the servo cylinder is measured, the measured pressure is compared with the preset pressure, and if the measured pressure is lower than the preset pressure, leakage of brake fluid is proved. However, the above leak detection method cannot accurately calculate the brake fluid leak amount.

Disclosure of Invention

The present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a brake fluid leakage detection method, which can accurately calculate the leakage amount of brake fluid and ensure the safe operation of a brake system of a vehicle.

The invention further provides a vehicle controller and a vehicle for executing the brake fluid leakage detection method.

According to a first aspect of an embodiment of the present invention, a brake fluid leakage detection method is applied to a vehicle having an integrated brake control system with a servo cylinder and a brake pedal, the detection method including:

When the brake pedal is stepped on, acquiring a first actual pressure of the servo cylinder;

When the first actual pressure rises to a preset pressure, acquiring a first hydraulic volume of the servo cylinder and a first moment;

acquiring a second actual pressure of the servo cylinder when the brake pedal is released;

when the second actual pressure is reduced to the preset pressure, acquiring a second hydraulic capacity and a second moment of the servo cylinder;

Obtaining a first brake fluid leakage amount according to the first hydraulic volume, the second hydraulic volume, the first moment, the second moment and a system hysteresis liquid required amount, wherein the system hysteresis liquid required amount is obtained by preset data of the vehicle, and the system hysteresis liquid required amount is used for representing the volume of the brake fluid output by the servo cylinder when the pressure of the servo cylinder reaches the preset pressure.

The brake fluid leakage detection method provided by the embodiment of the invention has at least the following beneficial effects: when a driver presses a brake pedal to control an integrated brake control system to brake a vehicle, acquiring a first actual pressure of a servo cylinder, determining a target pressure of the servo cylinder by the pressed depth of the brake pedal, acquiring a first hydraulic volume of the servo cylinder when the first actual pressure reaches a preset pressure in the process of lifting the first actual pressure of the servo cylinder to the target pressure, recording a first moment, and gradually lifting the first actual pressure to the target pressure; after a driver releases a brake pedal, the second actual pressure of the servo cylinder is gradually reduced, and when the second actual pressure falls back to the preset pressure in the process of gradually reducing the second actual pressure of the servo cylinder, the second hydraulic volume of the servo cylinder is acquired, and a second moment is recorded; presetting the hysteresis liquid demand of a system when a vehicle leaves a factory, and pumping out the brake liquid to a brake by a servo cylinder of an integrated brake control system to be the hysteresis liquid demand of the system when the pressure of the servo cylinder is equal to the preset pressure; according to the first hydraulic volume, the second hydraulic volume and the system hysteresis liquid requirement, the volume of the leaked brake liquid in the integrated brake control system can be calculated, then the time for leaking the brake liquid is calculated according to the first moment and the second moment, and further the leakage quantity of the first brake liquid is obtained, the leakage quantity of the brake liquid can be accurately calculated, and the safe operation of the brake system of the vehicle is ensured.

According to some embodiments of the invention, the detection method further comprises:

when the brake pedal is stepped on, acquiring the actual hydraulic pressure volume and the third actual pressure of the servo cylinder;

obtaining a theoretical hydraulic volume according to the third actual pressure and a theoretical relation curve, wherein the theoretical relation curve is constructed by preset data of the vehicle and is used for representing the relation between the pressure of the servo cylinder and the hydraulic volume;

obtaining a second brake fluid leakage amount according to the actual hydraulic volume and the theoretical hydraulic volume;

and obtaining a third brake fluid leakage amount according to the first brake fluid leakage amount and the second brake fluid leakage amount.

According to some embodiments of the invention, the deriving the third brake fluid leakage amount from the first brake fluid leakage amount and the second brake fluid leakage amount includes:

The third brake fluid leakage amount is obtained by the following formula:

Q=K1×q1+K2×q2；

Wherein Q is a third brake fluid leakage amount, Q1 is the first brake fluid leakage amount, K1 is a first weight, Q2 is the second brake fluid leakage amount, and K2 is a second weight.

According to some embodiments of the invention, the obtaining a third brake fluid leakage amount according to the first brake fluid leakage amount and the second brake fluid leakage amount further includes:

And acquiring the current road condition of the vehicle and the lateral acceleration of the vehicle, and changing the numerical values of the first weight and the second weight according to the road condition and the lateral acceleration.

According to some embodiments of the invention, the deriving the second brake fluid leakage amount from the actual hydraulic volume and the theoretical hydraulic volume includes:

the second brake fluid leakage amount is obtained by the following formula:

q2=d(Va-Vb)/dt；

wherein q2 is the second brake fluid leakage amount, va is the actual hydraulic pressure volume, vb is the theoretical hydraulic pressure volume, and d (Va-Vb)/dt is the discrete data derivative of the difference between the actual hydraulic pressure volume and the theoretical hydraulic pressure volume.

And when the leakage amount of the third brake fluid is larger than or equal to a leakage amount threshold value, controlling an instrument or a central control screen of the vehicle to send a prompt to a driver.

Acquiring a stroke gradient of the brake pedal, an actual pressure of the servo cylinder and a pressure gradient of the servo cylinder;

Acquiring duration time when the stroke gradient is greater than 0, the pressure gradient is greater than 0, and the actual pressure is greater than a pressure threshold value;

determining that the brake pedal is depressed when the duration is greater than a time threshold;

The detection method further comprises the following steps:

And when the stroke gradient is less than or equal to 0, or the pressure gradient is less than or equal to 0, or the actual pressure is less than or equal to a pressure threshold value, determining that the brake pedal is released.

According to some embodiments of the invention, the acquiring the stroke gradient of the brake pedal, the actual pressure of the servo cylinder, and the pressure gradient of the servo cylinder includes:

the actual stroke of the brake pedal is obtained, the stroke gradient is obtained by carrying out discrete derivation on the actual stroke, and the pressure gradient is obtained by carrying out discrete derivation on the actual pressure.

According to some embodiments of the invention, the obtaining the first brake fluid leakage amount according to the first hydraulic volume, the second hydraulic volume, the first time, the second time, and the system hysteresis liquid demand includes:

The first brake fluid leakage amount is obtained by the following formula:

q1=(V2-V1-V0)/(T2-T1)；

Wherein q1 is the first brake fluid leakage amount, V1 is the first hydraulic volume, T1 is the first time, V2 is the second hydraulic volume, T2 is the second time, and V0 is the system hysteresis liquid demand.

According to some embodiments of the invention, the integrated brake control system has a brake, the system hysteresis fluid demand is obtained from preset data of the vehicle, comprising:

performing a pressure-volume characteristic bench test on the brake, controlling the brake to boost pressure, obtaining a boost pressure-volume characteristic curve of the brake, and controlling the brake to decompress, obtaining a decompression pressure-volume characteristic curve of the brake;

Obtaining a supercharging hydraulic volume according to the supercharging pressure volume characteristic curve and the preset pressure, and obtaining a depressurizing hydraulic volume according to the depressurizing pressure volume characteristic curve and the preset pressure;

obtaining the hysteresis liquid demand of the brake according to the pressurizing hydraulic volume and the depressurizing hydraulic volume;

obtaining the hysteresis liquid demand of the system according to the hysteresis liquid demand of a plurality of brakes.

A vehicle controller according to a second aspect of an embodiment of the present invention includes:

at least one processor;

And a memory storing instructions that, when executed by the at least one processor, perform the brake fluid leak detection method as described above.

The vehicle controller according to the embodiment of the invention has at least the following beneficial effects: the vehicle controller executes the brake fluid leakage detection method, according to the first hydraulic volume, the second hydraulic volume and the system hysteresis liquid requirement, the volume of the leaked brake fluid in the integrated brake control system can be calculated, then the time for leaking the brake fluid is calculated according to the first moment and the second moment, the leakage amount of the first brake fluid is further obtained, the leakage amount of the brake fluid can be accurately calculated, and the safe operation of the brake system of the vehicle is ensured.

A vehicle according to a third aspect of an embodiment of the present invention includes the vehicle controller according to the second aspect of the above embodiment.

According to the method, the vehicle controller is used for executing the brake fluid leakage detection, the volume of the leaked brake fluid in the integrated brake control system can be calculated according to the first hydraulic volume, the second hydraulic volume and the system hysteresis liquid requirement, then the time for leaking the brake fluid is calculated according to the first moment and the second moment, and further the first brake fluid leakage quantity is obtained, the brake fluid leakage quantity can be accurately calculated, and the safe operation of the brake system of the vehicle is ensured.

Because the vehicle adopts all the technical schemes of the vehicle controller in the above embodiments, the vehicle controller at least has all the beneficial effects brought by the technical schemes in the above embodiments, and the description thereof is omitted.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Drawings

FIG. 1 is a flow chart of a brake fluid leak detection method according to an embodiment of the present invention;

FIG.2 is a flow chart of obtaining a third brake fluid leakage amount in an embodiment of the present invention;

FIG. 3 is a flow chart of determining that a brake pedal is depressed in an embodiment of the present invention;

FIG. 4 is a flow chart of a determination that a brake pedal is released in an embodiment of the present invention;

FIG. 5 is a flow chart of obtaining the system hysteresis fluid demand in an embodiment of the present invention.

Detailed Description

Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.

In the description of the present invention, it should be understood that the terms front, rear, upper, lower, axial, circumferential, etc. indicate an orientation or a positional relationship based on that shown in the drawings, and are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the apparatus or element to be referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as limiting the present invention.

In the description of the present invention, plural means two or more, and greater than, less than, exceeding, etc. are understood to not include the present number, and the above, below, within, etc. are understood to include the present number. The description of the first and second is for the purpose of distinguishing between technical features only and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated or implicitly indicating the precedence of the technical features indicated.

In the description of the present invention, it should be noted that terms such as arrangement, installation, connection, etc. should be construed broadly, and those skilled in the art may reasonably determine the specific meaning of the foregoing terms in the present invention in combination with the specific content of the technical solution.

The following description of the embodiments of the present invention will be made with reference to the accompanying drawings, in which it is apparent that the embodiments described below are some, but not all embodiments of the invention.

The integrated brake control system is a line-control hydraulic brake system for providing assistance for a vehicle, and the pressure and displacement of a servo cylinder in the integrated brake control system can be obtained by measuring a self-contained pressure sensor and a motor angle sensor respectively, and then the hydraulic volume of the system is obtained by calculating the displacement of the servo cylinder.

Brake fluid is an important component in automotive braking systems, which is responsible for transmitting braking forces, ensuring that the vehicle can be decelerated and parked safely and stably. If the brake fluid leaks, the performance of the brake system is seriously affected, which may lead to an increase in the braking distance, a braking failure and even a vehicle runaway, thereby seriously threatening the life safety of drivers and passengers.

By means of the brake fluid leakage detection method, problems existing in a brake system can be found in time, and potential safety hazards are avoided. Once a leak is detected, the driver may immediately take appropriate action, such as parking checks, contact with maintenance sites, etc., to ensure that the vehicle is timely repaired, preventing the failure from expanding or causing more serious consequences.

Brake fluid leakage not only affects the braking effect, but may also cause damage to other components in the brake system. For example, leakage may cause overheating of the brake pump, increased wear of the brake disc and brake pads, and the like. By detecting and repairing the leakage problem in time, the service lives of the brake system and related components can be effectively prolonged, and the maintenance cost is reduced.

The proper operation of the brake system is critical to the driving experience of the driver. Leakage of brake fluid may cause problems such as abnormal brake pedal feel, slow brake response, etc., affecting the driver's driving confidence and comfort. Through timely detection and processing of leakage problems, normal operation of a braking system can be ensured, and driving experience is improved.

In the prior art, the integrated brake control system is pre-stored with preset pressures corresponding to the treaded depths of different brake pedals, when a driver treads the brake pedals to control the vehicle to brake, the corresponding preset pressures are adjusted according to the treaded depths of the brake pedals, the measured pressure of the servo cylinder is measured, the measured pressure is compared with the preset pressure, and if the measured pressure is lower than the preset pressure, leakage of brake fluid is proved.

In the prior art, the leakage of brake fluid is detected according to the difference value between the calibrated preset pressure and the measured pressure, and the leakage quantity cannot be accurately obtained. Because the pressure volume characteristics of the vehicle brake have deviation on different sample pieces, and the gap of the brake becomes larger under the working conditions of turning and the like in the running process of the vehicle, the pressure volume characteristics of the brake are inconsistent with calibration, and in addition, the possibility of air intake exists in the using process of a brake system, the detection method of the leakage quantity is easily influenced by the pressure volume change and the air content of the brake system, and the risk of misjudging the leakage problem exists.

A brake fluid leak detection method according to an embodiment of the present invention, which is applied to a vehicle having an integrated brake control system having a servo cylinder and a brake pedal, will be described with reference to fig. 1 to 5.

Referring to fig. 1, the brake fluid leakage detection method according to the embodiment of the present invention includes the following steps.

In step S100, when the brake pedal is depressed, a first actual pressure of the servo cylinder is acquired.

It will be appreciated that after the driver depresses the brake pedal, the integrated brake control system will brake the vehicle, causing the pressure in the slave cylinder to rise, and the first actual pressure will be measured by the slave cylinder's own pressure sensor, and will vary with the depth to which the driver depresses the brake pedal.

In step S200, when the first actual pressure rises to the preset pressure, a first hydraulic pressure volume of the servo cylinder and a first time are acquired.

And setting preset pressure in an integrated brake control system of the vehicle, recording the current moment as the first moment when the first actual pressure gradually rises and reaches the preset pressure, measuring the displacement of the servo cylinder through a motor angle sensor of the servo cylinder, and further calculating the first hydraulic volume of the servo cylinder.

Step S300, when the brake pedal is released, a second actual pressure of the servo cylinder is obtained.

It will be appreciated that after the driver releases the brake pedal, the integrated brake control system will release the vehicle's brakes, causing the pressure in the slave cylinder to drop, and the second actual pressure will be measured by the slave cylinder's own pressure sensor, and will gradually decrease as the time the brake pedal is released increases.

In step S400, when the second actual pressure is reduced to the preset pressure, the second hydraulic volume of the servo cylinder and the second time are obtained.

And setting preset pressure in an integrated brake control system of the vehicle, recording the current moment as a second moment when the second actual pressure gradually decreases and then falls back to the preset pressure, measuring the displacement of the servo cylinder through a motor angle sensor of the servo cylinder, and further calculating the second hydraulic volume of the servo cylinder.

And S500, obtaining the first brake fluid leakage amount according to the first hydraulic volume, the second hydraulic volume, the first moment, the second moment and the system hysteresis liquid requirement amount, wherein the system hysteresis liquid requirement amount is obtained by preset data of a vehicle, and is used for representing the volume of the brake fluid output by the servo cylinder when the pressure of the servo cylinder reaches the preset pressure.

It can be understood that under the pressure increasing working condition and the pressure reducing working condition, the hydraulic volume inside the servo cylinder can be changed, and the preset pressure is taken as a sampling condition; the servo cylinder obtains a first hydraulic volume when the first actual pressure reaches a preset pressure under a supercharging working condition; the servo cylinder obtains a second hydraulic volume when the second actual pressure reaches a preset pressure under a decompression working condition; in the process that the servo cylinder transmits the brake fluid under the pressure increasing working condition and the pressure reducing working condition, part of the brake fluid stays in a pipeline or a brake and other parts, when the pressure of the servo cylinder reaches the preset pressure under the pressure increasing working condition and the pressure reducing working condition through the whole vehicle test in the vehicle development stage, the brake fluid volume output by the servo cylinder under the pressure reducing working condition is subtracted from the brake fluid volume output by the servo cylinder under the pressure increasing working condition, and the difference is the hysteresis liquid requirement of the system.

In some embodiments, step S500, obtaining the first brake fluid leakage amount according to the first hydraulic volume, the second hydraulic volume, the first time, the second time, and the system hysteresis liquid demand, further includes the following steps.

Step S501, obtaining a first brake fluid leakage amount by the following formula:

q1=(V2-V1-V0)/(T2-T1)；

wherein q1 is the leakage amount of the first brake fluid, V1 is the first hydraulic volume, T1 is the first moment, V2 is the second hydraulic volume, T2 is the second moment, and V0 is the hysteresis liquid requirement of the system.

The first hydraulic volume V1, the second hydraulic volume V2 and the system hysteresis liquid demand V0 which are obtained by taking preset pressure as sampling conditions are used as conditions to judge whether the integrated brake control system leaks or not.

Normally, when the integrated brake control system is operating normally, the difference between the first hydraulic volume V1 and the second hydraulic volume V2 should be equal to the system hysteresis liquid demand V0.

Therefore, the first hydraulic volume V1, the second hydraulic volume V2 and the system hysteresis liquid demand V0 are used for calculating the volume of brake liquid leakage, then the difference between the first time T1 and the second time T2 is calculated as the brake liquid leakage time, the volume of brake liquid leakage is divided by the brake liquid leakage time to obtain the first brake liquid leakage q1, and the first brake liquid leakage q1 represents the leakage of an integrated brake control system of a vehicle in unit time.

Referring to fig. 1, in some embodiments, the brake fluid leakage detection method further includes the following steps.

In step S600, when the brake pedal is depressed, the actual hydraulic pressure volume of the servo cylinder and the third actual pressure are acquired.

It will be appreciated that both steps S100 and S600 are triggered when the driver depresses the brake pedal, i.e. steps S100 and S600 can run synchronously.

After the driver presses the brake pedal, the displacement of the servo cylinder is measured through a motor angle sensor of the servo cylinder, so that the actual hydraulic volume of the servo cylinder is calculated, and the actual hydraulic volume changes along with the change of the distance that the driver presses the brake pedal.

It will be appreciated that after the driver depresses the brake pedal, the integrated brake control system will brake the vehicle, causing the pressure in the slave cylinder to rise, and a third actual pressure is measured by the slave cylinder's own pressure sensor, and will vary with the depth to which the driver depresses the brake pedal.

And step S700, obtaining a theoretical hydraulic volume according to a third actual pressure and a theoretical relation curve, wherein the theoretical relation curve is constructed by preset data of the vehicle and is used for representing the relation between the pressure of the servo cylinder and the hydraulic volume.

Since step S100 and step S600 can be operated synchronously, the third actual pressure of the servo cylinder can be measured by the pressure sensor of the servo cylinder itself.

The theoretical relation curve is obtained by a vehicle development stage through a whole vehicle test, and in the test process, the pressure of the servo cylinder under different hydraulic volumes is measured by using a pressure sensor by changing the hydraulic volume of the servo cylinder, so that the relation curve between the pressure and the hydraulic volume is formed.

Thus, the corresponding hydraulic volume can be found in the theoretical relationship by the pressure. In the present embodiment, the corresponding theoretical hydraulic volume is found in the theoretical relationship according to the third actual pressure of the servo cylinder.

Step S800, obtaining the second brake fluid leakage amount according to the actual hydraulic volume and the theoretical hydraulic volume.

Because the theoretical hydraulic volume is based on theoretical data obtained by a whole vehicle test, in the running process of the vehicle, the displacement of the servo cylinder is measured by a motor angle sensor arranged on the servo cylinder, and the corresponding actual hydraulic volume is calculated.

In some embodiments, step S800, obtaining the second brake fluid leakage amount according to the actual hydraulic volume and the theoretical hydraulic volume, further includes the following steps.

Step S801, obtaining a second brake fluid leakage amount by the following formula:

q2=d(Va-Vb)/dt；

Where q2 is the second brake fluid leakage amount, va is the actual hydraulic pressure volume, vb is the theoretical hydraulic pressure volume, and d (Va-Vb)/dt is the discrete data derivative of the difference between the actual hydraulic pressure volume and the theoretical hydraulic pressure volume.

Normally, the actual hydraulic pressure volume Va should be equal to the theoretical hydraulic pressure volume Vb when the integrated brake control system is operating normally.

When the integrated brake control system has brake fluid leakage, the actual hydraulic volume Va is different from the theoretical hydraulic volume Vb, and the volume of the brake fluid leakage can be obtained by calculating the difference between the actual hydraulic volume Va and the theoretical hydraulic volume Vb.

And then acquiring the actual hydraulic volume Va and the theoretical hydraulic volume Vb at a plurality of different moments, and deriving the second brake fluid leakage q2 through discrete data.

Step S900, obtaining a third brake fluid leakage amount according to the first brake fluid leakage amount and the second brake fluid leakage amount.

The first brake fluid leakage amount and the second brake fluid leakage amount obtained in two ways can be calculated by defining different weights for the first brake fluid leakage amount and the second brake fluid leakage amount, so that the brake fluid leakage amount of the vehicle can be determined through the third brake fluid leakage amount.

And step S1000, when the leakage amount of the third brake fluid is larger than or equal to the leakage amount threshold value, controlling an instrument or a central control screen of the vehicle to send a prompt to a driver.

When the third brake fluid leakage exceeds the leakage threshold value, the brake fluid leakage of the vehicle is proved to exceed the limit of safe driving, so that an alarm prompt is required to be given to a driver, and the brake system is switched to single-pipeline brake pressure building in time to ensure the safety of the brake system.

When the warning prompt is carried out on the driver, the warning can be sent out by controlling the instrument or the central control screen on the vehicle, so that the driver can know the information that the leakage amount of the brake fluid exceeds the safety range from the instrument or the central control screen.

The single-pipeline brake pressure building is to build the brake pressure by controlling the whole vehicle brake through a set of connected pipelines by using a master cylinder.

Referring to fig. 2, step S900 of obtaining a third brake fluid leakage amount from the first brake fluid leakage amount and the second brake fluid leakage amount includes the following steps.

Step S910, obtaining a third brake fluid leakage amount by the following formula:

Q=K1×q1+K2×q2；

wherein Q is the third brake fluid leakage amount, Q1 is the first brake fluid leakage amount, K1 is the first weight, Q2 is the second brake fluid leakage amount, and K2 is the second weight.

It is understood that the first brake fluid leakage q1 and the second brake fluid leakage q2 can be independently used as the results of the vehicle brake fluid leakage, and the two calculation results of the first brake fluid leakage q1 and the second brake fluid leakage q2 respectively use different measurement data in the vehicle, so that the calculation results are necessarily affected by the measurement accuracy.

To reduce the influence of the measurement accuracy on the brake fluid leakage amount, a first weight K1 is defined for the first brake fluid leakage amount Q1, a second weight K2 is defined for the second brake fluid leakage amount Q2, and the third brake fluid leakage amount Q is calculated by weighting the first brake fluid leakage amount Q1 and the second brake fluid leakage amount Q2 calculated in the two ways.

The actual values of the first weight K1 and the second weight K2 can be obtained by adopting the detection method for testing and calibrating according to the development stage of the vehicle.

In step S920, the road condition of the current running of the vehicle and the lateral acceleration of the vehicle are obtained, and the values of the first weight K1 and the second weight K2 are changed according to the road condition and the lateral acceleration.

It will be appreciated that the road conditions when the vehicle is travelling may affect the operation of the four brakes of the vehicle, for example when the vehicle is travelling over a bumpy road, the wheels may jolt due to the bumpy road, causing the pistons of the brakes to be impacted back, i.e. the pressure required by the brakes to increase, thereby causing a change in the hydraulic volume of the servo cylinders, which may change the actual hydraulic volume measured and thus affect the second amount of brake fluid leakage q2.

For this reason, if the road bumps, the value of the second weight K2 is reduced.

Road images in front of the vehicle can be acquired through sensors of the vehicle, and road conditions can be analyzed through the road images.

It is also possible to acquire the running condition of the vehicle from the sensor inside the vehicle, and determine whether the vehicle is running on a bumpy road surface based on the running condition.

The lateral acceleration of the vehicle refers to acceleration of the vehicle perpendicular to the running direction of the vehicle during running of the vehicle due to a large turning angle. The lateral acceleration of the vehicle also affects the operation of the four brakes of the vehicle, and the steering angle of the wheels is large, so that the piston of the brake is impacted and returned, namely the pressure required by the brake is increased, and the hydraulic volume of the servo cylinder is changed, so that the measured actual hydraulic volume is changed, and the second brake fluid leakage q2 is affected.

For this reason, if the lateral acceleration of the vehicle exceeds the acceleration threshold value, the value of the second weight K2 is reduced. Of course, a plurality of different acceleration threshold values may be set according to the lateral acceleration, and a corresponding second weight K2 may be set for each acceleration threshold value.

The steering angle of the wheels can be obtained by a sensor of the vehicle, and the lateral acceleration is calculated according to the dead weight of the vehicle and the current running speed.

Of course, a sensor for measuring the lateral acceleration may be provided in the vehicle, and the lateral acceleration of the vehicle may be directly acquired.

Referring to fig. 3, the detection method further includes the following steps.

Step S110, a stroke gradient of the brake pedal, an actual pressure of the servo cylinder, and a pressure gradient of the servo cylinder are acquired.

The stroke and the acceleration of the brake pedal when the driver presses the brake pedal are measured through a pedal simulator or a stroke sensor, and the stroke gradient of the brake pedal is calculated through the stroke and the acceleration.

Or acquiring actual strokes of the brake pedal for a plurality of times, and performing discrete derivation on the actual strokes to obtain stroke gradients.

After the driver presses the brake pedal, the integrated brake control system brakes the vehicle, so that the pressure of the servo cylinder rises, the actual pressure is measured through the pressure sensor of the servo cylinder, and the actual pressure changes along with the depth of the driver pressing the brake pedal.

And acquiring actual pressures of the servo cylinder for a plurality of times, and performing discrete derivation on the actual pressures to obtain a pressure gradient.

In step S120, when the stroke gradient is greater than 0, the pressure gradient is greater than 0, and the actual pressure is greater than the pressure threshold value, the duration is obtained.

When the stroke gradient of the brake pedal is greater than 0, it is proved that the driver is stepping down on the brake pedal, rather than releasing the brake pedal upward.

When the pressure gradient of the servo cylinder is larger than 0, the pressure of the servo cylinder is proved to be rising, and the servo cylinder is in a supercharging working condition.

Because the actual pressure of the servo cylinder may be lower than the preset pressure when the driver steps on the brake pedal, a pressure threshold value needs to be set, so that the pressure threshold value is greater than or equal to the preset pressure, and the servo cylinder can reach the preset pressure under the supercharging working condition.

When the above three conditions are satisfied, it is proved that the driver depresses the brake pedal, and then the duration for which the brake pedal is depressed is obtained.

In step S130, when the duration is greater than the time threshold, it is determined that the brake pedal is depressed.

The time threshold is set, and when the duration of the driver's depression of the brake pedal exceeds the time threshold, the driver can be identified as the brake pedal is depressed.

Referring to fig. 4, the detection method further includes the following steps.

Step S310, a stroke gradient of the brake pedal, an actual pressure of the servo cylinder, and a pressure gradient of the servo cylinder are acquired.

The stroke and the acceleration of the brake pedal when the brake pedal is released are measured through a pedal simulator or a stroke sensor, and the stroke gradient of the brake pedal is calculated through the stroke and the acceleration.

After the driver releases the brake pedal, the integrated brake control system releases the vehicle brake, causing the pressure in the slave cylinder to drop, and the actual pressure is measured by the slave cylinder's own pressure sensor, and gradually decreases as the time the brake pedal is released increases.

In step S320, when the stroke gradient is equal to or less than 0, or the pressure gradient is equal to or less than 0, or the actual pressure is equal to or less than the pressure threshold value, it is determined that the brake pedal is released.

After determining that the brake pedal is depressed and acquiring corresponding data, it is necessary to determine whether the brake pedal is released.

When the stroke gradient of the brake pedal is less than or equal to 0, the driver is proved to release the brake pedal.

When the pressure gradient of the servo cylinder is larger than 0, the pressure of the servo cylinder is proved to be declining, the servo cylinder is in a decompression working condition, and the driver releases the brake pedal.

When the actual pressure of the servo cylinder does not reach the pressure threshold value, the driver is light to brake the pedal, and even if the stroke gradient of the brake pedal and the pressure gradient of the servo cylinder are larger than 0, the actual pressure of the servo cylinder is reduced below the preset pressure, so that the related data under the pressure reduction working condition can be acquired, and the driver can be considered to release the brake pedal.

Referring to fig. 5, in some embodiments, the integrated brake control system has a brake, and the system hysteresis liquid demand is obtained from preset data of the vehicle in step S500, including the following steps.

And S510, performing pressure-volume characteristic bench test on the brake, controlling the brake to boost pressure, obtaining a boost pressure-volume characteristic curve of the brake, and controlling the brake to decompress to obtain a decompression pressure-volume characteristic curve of the brake.

The pressure-volume characteristic bench test is carried out on front and rear brakes of the whole vehicle in the vehicle development stage, and the difference between the pressure-volume characteristic bench test and the attention point of the conventional pressure-volume characteristic is that the hysteresis volume characteristic of the front and rear brakes due to the compression rate of a friction plate and the like is obtained, the conventional brake pressure-volume characteristic bench test only needs to pay attention to the volume value when the pressure is increased, but the test needs to carry out two working conditions of pressure increasing and pressure reducing, and the pressure-increasing pressure volume characteristic under the pressure-increasing working condition and the pressure-reducing pressure volume characteristic curve under the pressure-reducing working condition are obtained.

And step S520, obtaining a supercharging hydraulic volume according to the supercharging pressure volume characteristic curve and the preset pressure, and obtaining a depressurizing hydraulic volume according to the depressurizing pressure volume characteristic curve and the preset pressure.

The method comprises the steps of acquiring a first hydraulic volume by taking a preset pressure as a measuring point under a pressurizing working condition, and acquiring a second hydraulic volume by taking the preset pressure as the measuring point under a depressurizing working condition; under the supercharging working condition, a corresponding supercharging hydraulic volume is found out in a supercharging pressure volume characteristic curve under the condition of preset pressure, wherein the supercharging hydraulic volume represents the volume of brake fluid required by a single brake of the vehicle when the pressure rises and reaches the preset pressure; and under the pressure-reducing working condition, a corresponding pressure-reducing hydraulic volume is found out in the pressure-reducing pressure volume characteristic curve under the condition of the preset pressure, wherein the pressure-reducing hydraulic volume represents the volume of brake fluid required by a single brake of the vehicle when the pressure of the single brake drops and reaches the preset pressure.

In step S530, the hysteresis liquid demand of the brake is obtained according to the pressurized hydraulic volume and the depressurized hydraulic volume.

Subtracting the pressurized hydraulic volume from the depressurized hydraulic volume yields the hysteresis liquid demand of the individual brake.

In step S540, the system hysteresis liquid demand is obtained according to the hysteresis liquid demands of the plurality of brakes.

The hysteresis liquid demand of the four brakes of the vehicle can be obtained by summing the hysteresis liquid demand of the four brakes of the vehicle.

For example, by interpolating the target pressure P0 for the boost pressure-volume characteristic of the boost condition, the boost hydraulic volume Vinc corresponding to the boost condition; and (3) carrying out target pressure P0 interpolation on a pressure-relief pressure volume characteristic curve of the pressure-relief working condition, and reducing the corresponding pressure-relief hydraulic volume Vdec.

Subtracting the pressure-reducing hydraulic volume Vdec from the pressure-increasing hydraulic volume Vinc to obtain Vhyst, wherein Vhyst is the hysteresis liquid demand of a single brake, and summing the hysteresis liquid demands of four brakes to obtain the system hysteresis liquid demand V0, namely:

Vhyst1=Vdec1-Vinc1；

Vhyst2=Vdec2-Vinc2；

Vhyst3=Vdec3-Vinc3；

Vhyst4=Vdec4-Vinc4；

V0=Vhyst1+Vhyst2+Vhyst3+Vhyst4。

Wherein Vhyst1 is the hysteresis liquid demand of the first brake, vdec1 is the pressure-reducing hydraulic volume of the first brake, vinc is the pressure-increasing hydraulic volume of the first brake; vhyst2 is the hysteresis liquid demand of the second brake, vdec2 is the pressure-reducing hydraulic volume of the second brake, vinc is the pressure-increasing hydraulic volume of the second brake; vhyst3 is the hysteresis liquid demand of the third brake, vdec3 is the pressure-reducing hydraulic volume of the third brake, vinc is the pressure-increasing hydraulic volume of the third brake; vhyst4 is hysteresis liquid demand of the fourth brake, vdec4 is pressure-reducing hydraulic volume of the fourth brake, vinc is pressure-increasing hydraulic volume of the fourth brake; v0 is the system hysteresis liquid demand.

According to the brake fluid leakage detection method, the pressure and displacement of the servo cylinder in the integrated brake control system can be obtained through measurement of the pressure sensor and the motor angle sensor, and the hydraulic volume of the system can be obtained through calculation of the displacement of the servo cylinder.

The system leakage amount detection is performed in the following two ways.

In the first way, each time the driver has a process of stepping on and releasing the brake, at this time, the pressure volume and corresponding time of stepping on and releasing the brake are recorded, the volume difference of the driver's brake is obtained by subtracting the brake fluid hysteresis volume of the brake from the hydraulic volume difference of the releasing and stepping on the brake under a specific target pressure, and then the first brake fluid leakage amount in the loop is calculated by dividing the time difference between the step of releasing the brake and the step of stepping on the brake to the target pressure.

In the second mode, a driver continuously monitors the pressure volume of a braking system in the braking process, obtains the servo cylinder volumes corresponding to different braking pressures in real time, obtains a displacement difference value by making a difference between the servo cylinder volumes and the calibrated pressure volumes, and obtains the second brake fluid leakage amount by deriving the displacement difference value.

Different weights are defined for the leakage amount obtained in the two modes respectively, the leakage amount of the third brake fluid is calculated, and when the leakage amount of the third brake fluid reaches a leakage amount threshold value, alarming prompt and single-pipeline brake pressure building are needed to be carried out on a driver to ensure the safety of a brake system.

The brake fluid leakage detection method has important significance in the aspects of guaranteeing running safety, preventing brake system damage, improving driving experience and the like.

Specifically, referring to fig. 1, the brake fluid leak detection method of the present embodiment includes the following steps.

After the driver presses the brake pedal, the integrated brake control system brakes the vehicle, so that the pressure of the servo cylinder rises, the first actual pressure is measured through the pressure sensor of the servo cylinder, and the first actual pressure changes along with the depth of the driver pressing the brake pedal.

After the driver releases the brake pedal, the integrated brake control system releases the vehicle brake, causing the pressure in the slave cylinder to drop, and a second actual pressure is measured by the slave cylinder's own pressure sensor, and the second actual pressure gradually decreases as the time the brake pedal is released increases.

Under the pressure increasing working condition and the pressure reducing working condition, the hydraulic volume inside the servo cylinder can be changed, and the preset pressure is used as a sampling condition. The servo cylinder obtains a first hydraulic volume when the first actual pressure reaches a preset pressure under a supercharging working condition; the servo cylinder obtains a second hydraulic volume when the second actual pressure reaches a preset pressure under a decompression working condition; in the process that the servo cylinder transmits the brake fluid under the pressure increasing working condition and the pressure reducing working condition, part of the brake fluid stays in a pipeline or a brake and other parts, when the pressure of the servo cylinder reaches the preset pressure under the pressure increasing working condition and the pressure reducing working condition through the whole vehicle test in the vehicle development stage, the brake fluid volume output by the servo cylinder under the pressure reducing working condition is subtracted from the brake fluid volume output by the servo cylinder under the pressure increasing working condition, and the difference is the hysteresis liquid requirement of the system.

The first brake fluid leakage amount q1 is obtained by the following formula: q1= (V2-V1-V0)/(T2-T1), the first hydraulic volume is V1, the second hydraulic volume is V2, the system hysteresis liquid demand is V0, the first time is T1, and the second time is T2.

After the driver depresses the brake pedal, the integrated brake control system brakes the vehicle, thereby increasing the pressure of the servo cylinder, and the third actual pressure is measured by the pressure sensor provided in the servo cylinder, and is changed according to the depth of the driver depressing the brake pedal.

The second brake fluid leakage amount is obtained by the following formula: q2=d (Va-Vb)/dt. The second brake fluid leakage amount is q2, the actual hydraulic pressure volume is Va, the theoretical hydraulic pressure volume is Vb, and d (Va-Vb)/dt is discrete data derivative of the difference between the actual hydraulic pressure volume and the theoretical hydraulic pressure volume.

The third brake fluid leakage amount is obtained by the following formula: q=k1×q1+k2×q2.

The third brake fluid leakage amount is Q, the first weight is K1, and the second weight is K2.

When the third brake fluid leakage Q exceeds the leakage threshold value, the brake fluid leakage of the vehicle is proved to exceed the limit of safe driving, so that an alarm prompt is required to be given to a driver, and the brake system is switched to single-pipeline brake pressure building in time to ensure the safety of the brake system.

In addition, an embodiment of the present invention further provides a vehicle controller, including: at least one processor; and a memory storing instructions that, when executed by the at least one processor, perform the brake fluid leak detection method of the above-described embodiment.

The processor and memory in the vehicle controller may be connected by a bus, for example. The memory, as a non-transitory computer readable storage medium, may be used to store non-transitory software programs as well as non-transitory computer executable programs. In addition, the memory may include high-speed random access memory, and may also include non-transitory memory, such as at least one disk memory, flash memory device, or other non-transitory solid state storage device. In some embodiments, the memory optionally includes memory remotely located relative to the control processor, which may be connected to the controller via a network.

The non-transitory software program and instructions required to implement the detection method of the above-described embodiments are stored in the memory, and when executed by the processor, the detection method of the above-described embodiments is performed, for example, the method steps S100 to S1000 in fig. 1, the method steps S910 to S920 in fig. 2, the method steps S110 to S130 in fig. 3, the method steps S310 to S320 in fig. 4, the method steps S510 to S540 in fig. 5, and the like described above are performed.

The above described apparatus embodiments are merely illustrative, wherein the units illustrated as separate components may or may not be physically separate, i.e. may be located in one place, or may be distributed over a plurality of network elements. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

The embodiment of the invention also provides a vehicle, which comprises the vehicle controller of the embodiment. The vehicle may be a private car such as a sedan, SUV, MPV, or a pick-up card. The vehicle may also be an operator vehicle such as a minibus, bus, minivan or large trailer, etc. The vehicle can be an oil vehicle or a new energy vehicle. When the vehicle is a new energy vehicle, the vehicle can be a hybrid vehicle or a pure electric vehicle.

In the several embodiments provided by the present application, it should be understood that the disclosed apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the above-described division of units is merely a logical function division, and there may be another division manner in actual implementation, for example, a plurality of units or components may be combined or may be integrated into another system, or some features may be omitted, or not performed.

The units described above as separate components may or may not be physically separate, and components shown as units may or may not be physical units, may be located in one place, or may be distributed over a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.

In addition, each functional unit in the embodiments of the present application may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit. The integrated units may be implemented in hardware or in software functional units.

The integrated units, if implemented in the form of software functional units and sold or used as stand-alone products, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present application may be embodied in essence or a part contributing to the prior art or all or part of the technical solution in the form of a software product stored in a storage medium, including multiple instructions to cause a computer device (which may be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method of the various embodiments of the present application. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-only memory (ROM), a Random Access Memory (RAM), a magnetic disk, or an optical disk, or other various media capable of storing a program.

The embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention within the knowledge of one of ordinary skill in the art.

Claims

1. A brake fluid leak detection method for a vehicle having an integrated brake control system with a service cylinder and a brake pedal, comprising:

2. The brake fluid leak detection method according to claim 1, characterized in that the detection method further comprises:

3. The brake fluid leakage detection method according to claim 2, wherein the obtaining a third brake fluid leakage amount from the first brake fluid leakage amount and the second brake fluid leakage amount includes:

The third brake fluid leakage amount is obtained by the following formula:

Q=K1×q1+K2×q2；

4. The brake fluid leakage detection method according to claim 3, wherein the obtaining a third brake fluid leakage amount from the first brake fluid leakage amount and the second brake fluid leakage amount further includes:

5. The brake fluid leakage detection method according to claim 2, wherein the obtaining a second brake fluid leakage amount from the actual hydraulic pressure volume and the theoretical hydraulic pressure volume includes:

the second brake fluid leakage amount is obtained by the following formula:

q2=d(Va-Vb)/dt；

6. The brake fluid leak detection method according to claim 2, characterized in that the detection method further comprises:

7. The brake fluid leak detection method according to claim 1, characterized in that the detection method further comprises:

The detection method further comprises the following steps:

8. The brake fluid leak detection method according to claim 7, characterized in that the acquiring the stroke gradient of the brake pedal, the actual pressure of the servo cylinder, and the pressure gradient of the servo cylinder includes:

9. The brake fluid leakage detection method according to claim 1, wherein the obtaining the first brake fluid leakage amount from the first hydraulic volume, the second hydraulic volume, the first time, the second time, and the system hysteresis liquid demand includes:

The first brake fluid leakage amount is obtained by the following formula:

q1=(V2-V1-V0)/(T2-T1)；

10. The brake fluid leakage detection method according to claim 1, wherein the integrated brake control system has a brake, the system hysteresis fluid demand is acquired from preset data of the vehicle, comprising:

11. A vehicle controller, characterized by comprising:

at least one processor;

And a memory storing instructions that, when executed by the at least one processor, perform the brake fluid leak detection method according to any one of claims 1 to 10.

12. A vehicle comprising the vehicle controller of claim 11.